This invention relates to a water vehicle of the type which may be used on the surface or under water, either manned or unmanned, for propelling the vehicle to underwater locations, and more particularly to a powered underwater vehicle in which the pressure is substantially equalized in certain parts of the vehicle as the vehicle descends to greater depths in the water. The invention provides a way of preventing water from entering into the cavities of components, such as a motor, motor housing and switches which may be surrounded by water under great pressure at, for example, dive depths.
This invention is an improvement in an underwater vehicle such as the vehicle described and claimed in my U.S. Pat. No. 6,065,419 dated May 23, 2000 and entitled Underwater Dive Vehicle and in my pending U.S. patent application Ser. No. 09/909,568 filed Jul. 20, 2001. In that patent and pending application there is disclosed and claimed a dive vehicle which employs a flexible and resilient gas filled buoyancy element which may be in the form of a resilient bladder or a closed cell resilient sponge material, and may incorporate a plurality of rigid, foamed substantially incompressible second buoyancy elements that may be selectively attached to or removed from the vehicle to adjust buoyancy and thereby achieve neutral buoyancy according to the weight of the vehicle and its load and/or according to the buoyancy of the waters surrounding the vehicle.
Small powered underwater dive vehicles for taking one or two divers to underwater locations usually comprise a motor having a drive shaft which is operably connected to a propeller, a battery for energizing the motor and one or more control switches for selectively energizing the motor. Such devices are illustrated and described, for example, in U.S. Pat. No. 5,379,714, U.S. Pat. No. 4,864,959 and U.S. Pat. No. 4,996,938. Such vehicles, however, have encountered problems of leakage which is a particular problem when the vehicle is taken to substantial depths where the pressure may be several atmospheres. For every 10 meters of descent in sea water, an additional atmosphere of pressure is placed on the vehicle and its parts. Thus, at a depth of 30 meters or approximately 100 feet, there are 4 atmospheres of pressure, and the pressure corresponding increases as greater depths are attained. Underwater dive vehicles should be designed to withstand 15 atmospheres of pressure or the pressure that would be encountered at a depth of 500 feet.
The greater the pressure, the more stress there is on the seals which are in place to keep water out of such areas as the motor, the motor housing and switches. U.S. Pat. No. 4,864,959 recognizes this problem and is directed to detecting leaks of sea water into the battery or motor compartments of underwater dive vehicles. That patent also suggests that water absorbing sheets be stuffed around mechanical parts and the battery and clutch compartments. Another moisture detection system for an underwater dive vehicle is disclosed in U.S. Pat. No. 4,996,938.
In an underwater vehicle it is desirable, if not essential not just to detect, but to prevent the sea water surrounding the vehicle from entering the sealed cavities of the vehicle, such as those cavities in the motor housing, motor and switches. My U.S. Pat. No. 6,065,419 suggests filling those cavities with a non-conductive and non-corrosive liquid, such as silicone grease or transformer oil. Since liquids are substantially non-compressible, seals which are positioned to prevent the entry of sea water into the cavities of the vehicle will be supported by the liquid in the interior of the cavity and will not be distorted by the pressure of the sea water acting through the seal against a compressible and thus non-supporting gas within the cavity. In other words, with liquid in the interior of the cavity, the seal will not be moved inwardly to an extent which would normally cause it to distort or stress and permit leakage of sea water into the cavity.
Even though the liquid within the cavities may not be perceptively compressible, there may be a difference in the external pressure at substantial dive depths and the initial internal pressure within the cavities, particularly those cavities which are large in size and may have minute entrapped gas. These internal and external pressures tend to equalize causing the internal pressure to increase to that of the ambient pressure at dive depths. Then when the vehicle surfaces the internal pressure within the cavities tends to again equalize to the atmospheric pressure at sea level, with the result of possible inward leakage at dive depths and outward leakage at the surface.
The protection of the motor from the entry of sea water at dive depths presents a unique problem. Heretofore, the entire effort was aimed at improving the seals to keep sea water out of the motor. These efforts have not been uniformly successful and this invention takes a completely different approach to this problem.
It is thus an object of the present invention to provide a solution to the water leaks which have heretofore plagued motors other housed operating equipment such as that used in underwater dive vehicles by so constructing the vehicle, motor or other housed equipment that the water tight seals are not placed under stress even when the unit is submerged to depths of several hundred feet.
It is also the object of this invention to provide a modified electric motor which is unaffected by surrounding water even under external pressures encountered at substantial dive depths.
The invention may be incorporated in any underwater vehicle, motor, or housed equipment. One type of under water vehicle is disclosed in U.S. Pat. No. 6,065,419 which includes a selectively energizable propulsion unit for forcibly driving said vehicle through the water, with the propulsion unit including at least one motor and a housing for the motor. The vehicle may contain buoyancy means such as a resilient gas filled buoyancy element and/or a rigid buoyancy element.
The propulsion unit may include an electric motor or motors which would normally have an output shaft on which is mounted a propeller. An electric storage battery supplies electric current for driving the motor. A manually operable switch, which may be in the form of a push-button or joystick or turn switch or toggle switch would permit the motor to be selectively energized by the diver-operator.
It is preferred that all electrical terminals, such as the terminals for the battery and the motor or motors be encased in a waterproof epoxy resin, so that the sea water will not come into contact with these terminals and cause corrosion. It is preferred that the terminals and battery connections be protected by epoxy as described and illustrated in my aforementioned pending application Ser. No. 09/909568.
Means is provided for preventing water from entering sealed cavities of the vehicle, such as those cavities in the motor or switches. This is accomplished by filling those cavities with a liquid, such as water or transformer oil or a combination of two or more liquids. Since liquids are substantially non-compressible, seals which are positioned to prevent the entry of sea water into the cavities of the vehicle will be supported by the liquid in the interior of the cavity and will not be distorted by the pressure of the sea water acting through the seal against a compressible and thus non-supporting gas within the cavity. In other words, with liquid in the interior of the cavity, the seal will not be moved inwardly to an extent which would normally cause it to distort or stress and permit substantial leakage of sea water into the cavity.
One feature of this invention is the provision of a mechanism for preventing the passage of liquid either into or out of a liquid filled cavity when there are variations between the internal and exterior pressures at various depths or at the surface. This prevents the intrusion of sea water inwardly into the housing at diving depths and also prevents any xe2x80x9cblow-backxe2x80x9d or outward leaking of the liquid within the housing when the vehicle surfaces and the external pressure is less.
This additional protection can be obtained by filling a cavity, such as that of the motor housing, with a non compressible liquid and providing a flexible and resilient tube, bladder, or diaphragm which is positioned between and is in fluid communication with both the liquid within the cavity and the surrounding water (or air) external of the cavity. This will tend to equalize the pressure inside and outside of the housing, thus protecting against any leakage into or out of the housing caused by a differential in pressure between that within the housing and that outside the housing. This feature can be employed with other sealed cavities of the vehicle.
Another feature of this invention is the protection of the motor from the entry of sea water in a unique way. The prior attempts at preventing water from leaking into the motor have centered around improving the seals. This invention takes a radically different approach. Since the seals will distort very little if there is liquid on both sides of the seal, it has been found that filling the motor with a liquid having low viscosity approaching that of water will prevent the entry of sea water past the seals and into the motor at all dive depths. The preferred liquid is water and the preferred water is distilled water. When the motor is filled with distilled water it will operate efficiently and eliminate the possibility of having surrounding sea water enter the motor even at substantial depths and under substantial pressures.
Pure water, i.e., water with little or no dissolved or dispersed minerals or other substances which would increase the conductivity of the water also works well as a , cavity-filling liquid. Distilled water or pure water will allow the electric motor to operate for about 70 hours, after which the motor can be opened for the installation of new brushes and replacement of the water. If antifreeze is added, the motor can be operated in freezing temperatures. Because of the low viscosity of water, there is little resistance on the moving parts of the motor, such as the armature. Less pure water can also be used, but the higher the dissolved or dispersed mineral or conductive particle content the greater the tendency to conduct and corrode, thereby lessening the running time of the motor. Liquids such as pure or distilled water has an additional advantage of cooling the motor.